Add authentication support to shuffle

patch by Aleksey Yeschenko; reviewed by Brandon Williams for
CASSANDRA-6484
CHANGES.txt whitespace
Merge branch 'cassandra-1.2' into cassandra-2.0

Conflicts:
	CHANGES.txt
Merge branch 'cassandra-2.0' into cassandra-2.1

Conflicts:
	CHANGES.txt
Merge branch 'cassandra-2.1' into trunk